Due to their unique properties of interacting with ions and solvents, polyelectrolytes have been used as key components for a wide range of biomedical, energy and environmental applications. Zwitterionic polyelectrolytes have balanced positive and negative charges and have been studied for use in drug delivery, biosensing and antimicrobial coatings and zwitterionic polymers having outstanding antifouling, antimicrobial, mechanical, optical and stability properties have been developed. Various zwitterionic polyelectrolytes have been found to have outstanding antifouling properties in resisting proteins, mammalian cells, and microbes, excellent in vivo biocompatibility, as well as the capability of further functionalization for applications in biosensing and drug delivery. However, existing zwitterionic polymers lack conductivity, optical properties, elasticity and quick response to physical stimuli, which limit their utility to address a broader range of challenges.
As a group of emerging biomaterials, conjugated polymers (CPs) have attracted significant interests for diagnosis, imaging, and therapy. In particular, CPs have attracted significant interests for numerous biomedical and biotech purposes, including bioelectronics and biosensing tissue engineering, wound healing, robotic prostheses, biofuel cell, etc., due to their great design flexibility, tunable conductivity, mechanical properties compatible with soft tissues and ease of fabrication over inorganic conducting or semiconducting materials. As core components in these devices, CPs improve communications between electrochemical devices and biological systems by allowing the delivery of smaller charges or the detection of very low electrical signals, so devices can perform more efficiently. However, biomacromolecules, such as proteins and lipids, tend to adsorb to hydrophobic CPs surfaces that are originally designed for non-biological and non-aqueous systems. The nonspecific adsorption of biomacromolecules on electrochemical device surfaces reduces the sensitivity and performance of the device and triggers foreign body response that eventually leads to the failure of implanted devices. In vivo studies have shown that the improved electrochemical performance of devices by CP coatings could not be sustained after implantation due to the formation of non-conductive scar tissues around devices.
Moreover, traditional conducting hydrogels are typically synthesized through either blending or physical crosslinking CPs with non-conducting polymeric hydrogel networks. Although these synthesis approaches are very easy and do not require long reaction time to achieve reasonable yields, non-conducting components can diminish electrochemical properties of conducting hydrogels. Secondly, physically crosslinked hydrogels are generally less stable and excessive crosslinking or doping metal ions reduce their biocompatibility. Thirdly, multiple components of a conducting hydrogel increase the difficulty of processing and micropatterning, which are important for fabricating hydrogel-based electronic devices. Furthermore, non-conducting components of current conducting hydrogels are not effective enough to prevent biofouling in the complex medium and foreign body response.
Accordingly, what is needed in the art is materials with high electrical conductivity, good biocompatibility, good stability, good non-fouling properties, and multi-functionality for allowing specific cell adhesion and proliferation.